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Unit 4 - Cells: The Working Units of Life
Transcript of Unit 4 - Cells: The Working Units of Life
1. Cell are the basic units of structure and function in living things.
2. All living things are made of cells.
3. All cells come from preexisting cells.
4. Metabolism occurs within cells.
5. Cells have genetic material.
6. The activity of an organism is based on the combined activity of its cells.
7. Similar organisms have similar cells.
Cells have to stay small. Why?
Volume - determines the amount of metabolic activity of a cell
Surface Area - determines the amount of materials that can enter or exit a cell
Why would it be a problem if the volume of a cell increases at a faster rate than surface area? Can this concept be applied to things besides cells?
How can we classify cells?
The presence of a nucleus is a great place to start!
What are the big differences? Do prokaryotes have any specialized structures, or are they basically a membrane surrounding some DNA floating in jelly?
DNA stored here (chromatin = DNA + histone proteins
site of DNA replication
site of transcription (DNA --> mRNA)
contains the nucleolus
ribosomes made here
can be found in the cytoplasm, attached to the RER, or inside other organelles (like mitochondria)
no matter where you find them, ribosomes have one job - protein synthesis (translation)
consist of two subunitis, made of rRNA and protein - macromolecular aggregate
folds add surface area to the interior of the cell
covered in ribosomes
add chemical tags to proteins for delivery to other parts of the cell (transportation)
folds up proteins into their tertiary structure
not covered in ribosomes
chemically modify things inside the cell, making them more polar (and therefore easier to break down)
some complex carbs start to be broken down here
site of lipid formation
made of two parts - flattened sacs called cisternae (cis side closer to nucleus, trans side closer to membrane), and vesicles
concentrates and packages proteins before they are sent to their destination
in plant cells, responsible for making parts of the cell wall
store and break down toxic substances (such as hydrogen peroxide)
breakdown of glucose to produce ATP
type of plastid
site of photosynthesis
convert solar energy to chemical energy
structure (turgor pressure)
controls direction of growth
allow for signaling between cells - plasmodesmata
Cell Support and Communication
Cytoskeleton - network of protein filaments inside the cell that:
support the cell
maintain cell shape
control the position of organelles
allow cytoplasm to move around
hold the cell in place by interacting with extracellular (outside of the cell) structures
3 types of materials make up the cytoskeleton:
- movement, shape
- made of protein called actin
- dynamic instability - parts of the cytoskeleton can be build up or broken down quickly (can help cytoplasm move around - amoeba, cytokinesis)
2. Intermediate filaments
- many different kinds
- don't break down easily
- anchor cell structures in place
- maintain rigidness in some tissues
- thick and hollow
- form a rigid internal skeleton
- allow movement of some proteins
- form structures like cilia, flagella